An Experimental Study About The Efficiency Of Seismoelectric Conversion On Core

The phenomenon of electromagnetic waves caused by movement of electriferous ions in lacunal liquid,when sound waves transmited on core,known as Seismoelectric Conversion Effect.In the study of seismology seismoelectric effect is called. Seismoelectric conversion effect is in the nature of the conversion of mechanical energy is converted to electrical energy, because it is closely related with the lacunal fluid's nature,and can provide a new method for resource exploration,so it has been attached great importance in the study of geophysics,and the research about it has never stopped. The method in practical applications over the years has not been able to become an effective and practical technology, the key problem is that the efficiency of seismoelectric conversion is extremely low, that is, the ratio of electrical energy converted by mechanical energy is very low, the converted electromagnetic signals is very weak, data acquisition is more difficult. In the past ten years, with the development of electronic technology and small-signal detection technology ,the problem about weak signal detection techniques in the study of seismoelectric conversion effect has been solved, the method has become hot spot in the field of geophysical research, many scholars at home and abroad have done effective exploration.In the current application of the seismoelectric conversion effect, the main areas is about seismic exploration, it has carried out extensive research,for solving the problem about the oil and gas exploration,from theoretical studies, laboratory analysis, physical models and field experiments have made significant progress ,the main problem is that the electromagnetic conversion efficiency is low, the geological conditions of seismic exploration is more complicated ,in the data acquisition and processing are more difficult to face. Effective method is that apply it in the well hole, solve the existent problems about electromagnetic conversion efficiency through theoretical and experimental, designed for the detection of lacunal liquid salinity and stratum permeability.In this paper, the theoretical study about seismoelectric conversion efficiency has been done, the rock seismoelectric conversion efficiency used in well hole to measure the salinity of lacunal liquid to determine stratum liquid property to directly detect the purpose of stratum liquid property, in order to developing a new logging method - Acoustic electric logging technology to provide experimental and theoretical basis. At the same time, this method can play an acoustic logging and electrical logging of the comprehensive advantages, acoustic and electric signals in the wells can be collected at the same time, it has great significance on the study of logging method, exploration applications to detect the nature of strata, as well as a comprehensive study of the reservoir, evaluation capacity.In this paper, we had collected and recognised the converted electromagnetic wave signals ,the results showed that the shape of the converted electromagnetic wave signals was similar to the acoustic wave, they were close to that in the frequency , in the frequency spectrum t he converted electromagnetic wave signals showed the characteristics of the two peaks, in the spread much faster than the speed of acoustic wave, the amplitude of change in salinity is more sensitive. Because of the size and data collection methods used in this paper were consistent with the actual logging tool,so can provide a reference for the development of logging tools.In this paper, the theory about electrochemical, porous media acoustics, electromagnetics, mathematics is applicated sufficiently, stratum wellbore liquid, logging equipment were described, taking into account the coupling phenomenon aroused by the relative movement of fluid and solid skeleton when sound waves transmit on core, excitated the converted electromagnetic waves,established a well hole seismoelectric conversion model, the formula is derived in detail and put forward to describe the two parameters of the characteristics of the converted electromagnetic waves, that is, the conversion amplitude and the characteristic time of electromagnetic waves, the conversion efficiency is calculated ,the relation of conversion efficiency and frequency is discussed. There is lower conversion efficiencyon core, the signal of converted electromagnetic waves is very weak, weak signal acquisition technology is needed technically on the experiment.In this paper, there has established a well hole seismoelectric conversion model on the base of the theoretical study, describing the characteristics of the parameters of the conversted electromagnetic waves, the conversion efficiency is calculated,and discussed the relation of conversion efficiency and frequency. In the experimental study, we had fully used electronic technology and small-signal detection technology, and completed seismoelectric conversion data acquisition in the simulated wells,and analysed the characteristics of the conversted electromagnetic waves,and studied the conversted electromagnetic waves's characteristics parameters and the relations of stratum water salinity and permeability.In this paper's experimental study, we had used river sand and cement to accumulate a simulative well according to a certain percentage, and the actual size was closed to the stratum ,and simulated effectively nature of the stratum, and fully used electronic technology and small-signal detection technology, thus ,wo had completed the seismoelectric conversion data acquisition on simulated well, at the same time we had collected the acoustic signals and electromagnetic signals, and had a correct handling on experimental data, analysed the characteristics of the converted electromagnetic signals, and established the conversted electromagnetic waves's characteristics parameters and the relations of stratum water salinity and permeability. The results from the study,there is a good linear relationship between the amplitude of conversted electromagnetic waves and the stratum water salinity .there is a sensitivere reaction about the changes, so the method is applied to logging technology, can provide a measurement method on measuring the stratum water nature and ascertaining the stratum water resistivity .In this paper,we had carried out a detailed study in theory about seismoelectric conversion efficiency on core, taking into account liquid in well ,logging equipment, stratigraphic response ,in the experimental study,we had consummated the weak signal detection technology on data acquisition of seismoelectric conversion efficiency on core.In this paper,we had researched the application of seismoelectric conversion efficiency in logging technology through two aspects of theoretical and experimental study,and provided a theoretical and experimental basis for developping acoustic electric logging equipment. If you want to work in this regard the development of logging tools ,you also need to further improve the accuracy of weak signal detection, and further improve the weak signal of the measurement techniques, translating theoretical and experimental research production into practical technology, we can provide services to the exploration and production.